This invention relates to a vehicle collision object discriminating apparatus for discriminating a collision object having collided with a vehicle.
For example, as disclosed in the Japanese Patent Application Laid-open No. 11-310095, it is conventionally known to discriminate a collision object collided with a vehicle, especially whether or not the collision object is a pedestrian. According to this prior art document, a sensor for generating an output in accordance with a detected impact force is disposed to each of the front and rear sides of a bumper. A combination pattern of these sensor outputs is compared with pre-memorized data to judge the type of a collision object. Using this collision object judging technique makes it possible to prevent a pedestrian protecting device, such as a pedestrian protecting airbag, from erroneously operating in such a case that the collision object is not a pedestrian.
However, a variety of collision objects generally include stationary objects fixed on the ground, pedestrians, and lightweight non-stationary objects including signboards (hereinafter, also referred to as lightweight stationary objects or lightweight fallen objects). Furthermore, the stationary objects are roughly classified into heavyweight stationary objects including concrete walls and lightweight stationary objects including standing poles. Hence, accurately discriminating these objects by merely relying on the combination of output levels of two impact force detection sensors is very difficult. For example, relying only on the combination of output levels of two impact force detection sensors makes it very difficult to discriminate a pedestrian from road traffic signs or comparable lightweight stationary objects having a relatively light weight compared with other stationary objects.
Furthermore, to secure satisfactory discrimination accuracy, it is generally necessary to divide each output of two impact force detection sensors into multistage (at least four stages) levels. To this end, the impact force detection sensor is inevitably an analog output type sensor. Thus, in practical aspect, the impact force detection sensor is complicated in arrangement, expensive in cost, and insufficient in reliability and durability.